*May 9, 2015*

# Calculating Time Through History

Measuring time has always been an important endeavor throughout human history. The first sundials relied on shadows to estimate the hour of the day, but they were not effective in cloudy weather or at night, and required adjustment as the seasons changed. A water clock was an early timekeeping device that measured time by regulating the flow of liquid from one vessel to another. The hourglass was able to measure elapsed time by the regulated trickle of sand and has become an almost universal symbol for time. The first mechanical clocks were invented in Europe in the 14th century and became the standard timekeeping device until the pendulum clock was invented in 1656. The invention of the mainspring in the early 15th century allowed portable clocks to be built, which evolved into the first pocket watches. Keeping track of elapsed time has always been an integral part of business, personal, and social relationships, which makes calculating time equally important whether you are an employee, an employer, an independent contractor, a student, an intern, or just about anyone needing to report time spent on different projects, jobs, activities, tasks, customers, or volunteer hours.

Although most of us are used to calculating time based on 60 minutes to an hour, this was not always the case in history. Leaders of the French Revolution divided the day into 10 decimal hours, each decimal hour into 100 decimal minutes, and each decimal minute into 100 decimal seconds. This came to be known as "French Revolutionary Time." The main advantage of a decimal time system is that since the base used to divide the time is the same as the one used to represent it, it is much easier to perform timestamp conversions. For example, 1:23 is one decimal hour and 23 decimal minutes, or 1.23 hours, or 123 minutes. Sexagesimal time, sometimes called "base 60," is the standard of time we are most familiar with, which divides the day into 24 hours, each hour into 60 minutes, and each minute into 60 seconds. It originated with the ancient Sumerians around 3,000 BC and is still used for measuring time, angles, and geographic coordinates. The number 60 has twelve factors, which simplifies fractions involving sexagesimal numbers. For example, one hour can be divided evenly into sections of 30 minutes, 20 minutes, 15 minutes, 12 minutes, 10 minutes, 6 minutes, 5 minutes, 4 minutes, 3 minutes, 2 minutes, and 1 minute. This makes it an effective method for calculating time.

Measuring the approximate amount of time elapsed is one thing, to get an accurate total of the hours, and even minutes and seconds involved, is quite another. This is why devices that actually perform the calculation between the start and stop time of an event are so important. A stopwatch measures the amount of time elapsed from when it is started to the time when it is stopped, and is either mechanical or digital. A time clock records the time an employee punches in and the time an employee punches out, but the amount of elapsed time between them must still be totaled for accurate payment of wages or billing of client time. Manually entering the start and stop times into a timecard calculator program can save you lots of effort because the totaling of time and converting it to decimal hours for entry into your payroll program is automatic.

Your time and attendance system should offer a lot of flexibility when it comes to calculating time. You should be able to decide what options to include on each report and how hours and overtime are totaled. You should also be able to display total hours worked as decimal hours or hours & minutes. When you see timecard totals with a "." separator between the hours and minutes, it is in decimal format, which is based on units of 10 and how most payroll programs expect the hours. When you see timecard totals with a ":" separator, it is in hours & minutes format, which is based on units of 60. It is a small setting but it can make a big difference in how you interpret your employee timecards. The usual scenario goes something like this. You have totaled the hours on a calculator and come up with a small difference to what is listed on the employee timecard. This is the result of converting time (hours & minutes) to decimal format. For example, :20 (20 minutes) is converted to .33 (20 divided by 60). If you add up :20 + :20 + :20 you get 1 hour. If you add up .33 + .33 + .33 you get .99 hours. The conversion of time to decimal should be based on the total hours & minutes so it is always 100% accurate rather than doing the decimal conversion on each entry and totaling them up individually, which leads to the difference you are seeing. Calculating time does not have to be a labor intensive project when you have the right tools in place, which includes an efficient time and attendance software program for totaling time.

Although most of us are used to calculating time based on 60 minutes to an hour, this was not always the case in history. Leaders of the French Revolution divided the day into 10 decimal hours, each decimal hour into 100 decimal minutes, and each decimal minute into 100 decimal seconds. This came to be known as "French Revolutionary Time." The main advantage of a decimal time system is that since the base used to divide the time is the same as the one used to represent it, it is much easier to perform timestamp conversions. For example, 1:23 is one decimal hour and 23 decimal minutes, or 1.23 hours, or 123 minutes. Sexagesimal time, sometimes called "base 60," is the standard of time we are most familiar with, which divides the day into 24 hours, each hour into 60 minutes, and each minute into 60 seconds. It originated with the ancient Sumerians around 3,000 BC and is still used for measuring time, angles, and geographic coordinates. The number 60 has twelve factors, which simplifies fractions involving sexagesimal numbers. For example, one hour can be divided evenly into sections of 30 minutes, 20 minutes, 15 minutes, 12 minutes, 10 minutes, 6 minutes, 5 minutes, 4 minutes, 3 minutes, 2 minutes, and 1 minute. This makes it an effective method for calculating time.

Measuring the approximate amount of time elapsed is one thing, to get an accurate total of the hours, and even minutes and seconds involved, is quite another. This is why devices that actually perform the calculation between the start and stop time of an event are so important. A stopwatch measures the amount of time elapsed from when it is started to the time when it is stopped, and is either mechanical or digital. A time clock records the time an employee punches in and the time an employee punches out, but the amount of elapsed time between them must still be totaled for accurate payment of wages or billing of client time. Manually entering the start and stop times into a timecard calculator program can save you lots of effort because the totaling of time and converting it to decimal hours for entry into your payroll program is automatic.

Your time and attendance system should offer a lot of flexibility when it comes to calculating time. You should be able to decide what options to include on each report and how hours and overtime are totaled. You should also be able to display total hours worked as decimal hours or hours & minutes. When you see timecard totals with a "." separator between the hours and minutes, it is in decimal format, which is based on units of 10 and how most payroll programs expect the hours. When you see timecard totals with a ":" separator, it is in hours & minutes format, which is based on units of 60. It is a small setting but it can make a big difference in how you interpret your employee timecards. The usual scenario goes something like this. You have totaled the hours on a calculator and come up with a small difference to what is listed on the employee timecard. This is the result of converting time (hours & minutes) to decimal format. For example, :20 (20 minutes) is converted to .33 (20 divided by 60). If you add up :20 + :20 + :20 you get 1 hour. If you add up .33 + .33 + .33 you get .99 hours. The conversion of time to decimal should be based on the total hours & minutes so it is always 100% accurate rather than doing the decimal conversion on each entry and totaling them up individually, which leads to the difference you are seeing. Calculating time does not have to be a labor intensive project when you have the right tools in place, which includes an efficient time and attendance software program for totaling time.